1. Field of the Invention
The present invention relates to the field of sport-specific movement. More specifically, the present invention relates to such movement obtained through the use of an exercise-apparatus. More specifically still, the present invention relates to such movement that biomechanically duplicates the movement of the xe2x80x9cdouble-polingxe2x80x9d technique in cross-county skiing.
2. Description of Related Art
There are two basic forms of cross-country skiing: modern xe2x80x9cskatingxe2x80x9d style; and traditional style. The modern skating style requires both arms to move together 99% of the time, and hence is characterized as xe2x80x9cdouble-poling.xe2x80x9d In traditional style cross-country skiing, both double-poling and single-polingxe2x80x94where the arms move in alternationxe2x80x94are used. Various methods and devices have previously endeavored to provide skiers with a way to duplicate the movements an athlete performs during cross-country skiing. Virtually all previous references have been directed to devices with which a person simulates only the single-poling style. These devices have been such that a person pulls with each hand in alternation on separate handles or poles while the person""s legs slide or step in alternation, so as to mimic a cross-country skiing stride of the single-poling technique.
An example of a cross-country ski exercise apparatus which is directed to single-poling is taught by Stropkay (U.S. Pat. No. 4,659,077; 1987). The Stropkay apparatus has two longitudinal rails on which are positioned a pair sliding foot-supports. These foot-supports restrain the feet of a person who is using the apparatus from moving laterally. A consequence of this lateral restraint is that the muscles in the person""s hip, legs, lower back and abdomen do not support and coordinate the movement of the legs to the degree that they would during xe2x80x98realxe2x80x99 cross-county skiing. The Stropkay apparatus also provides a stomach support for a person exercising on the apparatus. This is unfortunate, since this stomach support diminishes the stabilizing function normally required of the muscles of the stomach and lower back during actual cross-country skiing, thus failing to strengthen this critical link in the required movement. To simulate the striding technique of cross-country skiing, the Stropkay apparatus provides the user with two handles, each attached to one end of a cable that is fitted around a pulley. This arrangement provides the user with only a reciprocating movement for the arms and not the tandem arm movement in the same direction that is essential to the double-poling technique used in cross-country skiing. This reciprocating arm movement further militates against the use of the Stropkay apparatus for double-poling technique.
Marshall (U.S. Pat. No. 4,743,015; 1988) and Chi (U.S. Pat. No. 5,299,996; 1994) each teach a ski-simulator device that is similar to the invention of Stropkay. Common to the Marshall and Chi invention is a pair of foot-supports that slide in a reciprocating fashion along support rails. These foot-supports, because they prevent side-to-side movement, reduce the stabilizing demand on the muscles of the abdomen, back and hip in the same way that the Stropkay apparatus does. The chief difference between the devices of Marshall and Chi in comparison to Stropkay is that the Marshall and Chi devices provide pivotably disposed poles for reciprocating hand-arm movement, whereas the Stropkay invention uses a rope and pulley system. Though the structure is different, the effect on a person who uses the devices is the same: the hands and arms are constrained to reciprocating movement. Consequently, the Marshall and Chi devices are also inappropriate for practice with double-poling.
Another device similar to that of Stropkay is taught by Feuer et al. (U.S. Pat. No. 4,960,276; 1990). The Feuer et al. device also constrains the legs to movement in longitudinal slots, with no lateral movement possible. Thus, Feuer et al. shares the drawbacks of the previously mentioned invention for use as a double-poling exercise device.
A previous skiing-simulation device that does not constrain a user""s feet to purely longitudinal movement is that of Neuberg et al. (U.S. Pat. No. 5,536,225; 1996). The Neuberg et al. device, however, is directed toward the movement and techniques of downhill skiing. Consequently, that device, while including poles with handles for a user to grip, does not provide for any movement of these poles. A tandem movement of the arms, as was previously stated, is essential for the double-poling technique of cross-country skiing. An additional attribute of the Neuberg at al. device that renders it unsuitable for use for double-poling is that the device does not provide for any longitudinal movement of the feet relative to the poles. The movement of the arms longitudinally in unison in relation to the feet is essential to the double-poling technique of cross-country skiing.
Therefore what is needed is a device that enables a person to emulate the actual biomechanical motion of the double poling technique of cross-country skiing.
The present invention provides a method and apparatus with which a person can perform the optimal biomechanical movement used in the double-poling technique of cross-country skiing. The present invention additionally provides a method and apparatus for performing this optimal biomechanical movement in conjunction with certain commercially available rowing machines.
The apparatus of the present invention includes dual hand grips that are connected by a connector to a resistance force generator that acts against the user pulling on the dual hand grips. The connection, as provided by the connector, between the resistance force-generator and the dual hand grips is such that the force a user gripping the dual hand grips pulls against is always directed up from and in front of the user. Most importantly, the dual hand grips of the present invention allow the user to begin a movement cycle with the hands forward of the plane of his or her body and following a smooth continuous movement of both arms in unison, to end with the hands behind the body plane.
In one class of embodiments, the dual hand grips are at the end points of a unitary, U-shaped handle, the concave side of which faces the user. All embodiments of the present invention share the essential quality that the user is able to pull the hands from a position high and in front relative to the shoulders to a position behind the midline (from a side perspective) of the body, something that is impossible to accomplish with a handle having a straight shape. For example, the double-poling handle of the present invention may include two separate ropes, each having a handle on one end. Alternatively, the double-poling handle can include a single section of rope having a hand grip on each end, the section of rope being connected near its middle point to the apparatus.
The force may be supplied by any of the constant or variable resistance force generators used in the exercise-machine field. A non-exhaustive list includes weight-plates, elastomers, flywheels having a bladed fan as a braking means, and fluid dampeners. The magnitude of the force may vary with either the displacement of the hand grips or the speed with which the hand grips are moved. The connector between the dual hand grips and the force generator is typically one or more cables, though other suitably strong and flexible connectors may be used within the scope of the present invention. In the Preferred Embodiment the resistance force generator and the connector are provided by a stationary-rowing machine that has been placed in an upright orientation, while the dual hand grips are part of a U-shaped handle.
The method of the present invention takes advantage of the fact that some stationary-rowing machines already incorporate many of the elements needed for the apparatus of the present invention. The method then consists of converting an existing stationary-rowing machine by orienting it in a vertical position so that the section of the machine that normally is in front of a seated xe2x80x9crowerxe2x80x9d is now ahead of and above the standing xe2x80x9cskier.xe2x80x9d At that point the dual hand grips are used to replace the xe2x80x9coarxe2x80x9d grip simulators of the stationary-rowing machine. An essential aspect of the conversion of the stationary-rowing machine is the positioning so that the xe2x80x9coriginxe2x80x9d of the stationary-rowing machine""s flexible connector is placed above shoulder-height of the user. By xe2x80x9coriginxe2x80x9d, what is meant is the point where the connector separates, on its path to the dual hand grips, from the exercise apparatusxe2x80x94which in the case of the Preferred Embodiment is a pre-existing stationary-rowing machine. A second essential aspect of the method of the present invention is the use of the dual hand grips of the present invention. In the Preferred Embodiment, these hand grips are interlocked over the handle of a pre-existing stationary-rowing machine. In an exemplary embodiment of the present invention, a further step includes performing the double-poling technique with the adapted stationary rowing-machine. Thus, the method of the present invention makes use of the apparatusxe2x80x94in any of its embodimentsxe2x80x94of the present invention.
To use this adapted stationary rowing-machine for the double-poling technique, a person stands facing the converted apparatus. The user""s left and right hands each grip one end component of the dual hand grip. The user stands with knees slightly flexed and with back basically straight. In a starting position, the arms are extended forward and upward of the shoulders, parallel to one another, with the elbows partially bent, resulting in the person""s latissimus dorsi muscles being almost fully extended. (In describing this motion, it is helpful to think of the user""s arms as pendulums.) Next, the user pulls the dual hand grips in an arcing motion downward and backward, while the arms simultaneously straighten. During this movement, the linked systems of hip and abdominal flexors, in conjunction with the latissimus dorsi, posterior deltoids and triceps, move the arms/hands toward the knees and thence past the body mid-line (from a perspective to either side of the person) in a forceful pendulum motion. Because the double-poling grips go on either side of the user, the user""s hands can be brought to a finishing position behind his or her midline. This allows for optimal force transfer during the double-poling technique and would correspond to the maximum speed that an individual could obtain using the technique during actual skiing. For an additional description on this double-poling technique and the biomechanics involved, see Richard Taylor, The Top Half, Winter 1986 THE PROFESSIONAL SKIER 19.
Three key aspects of the present invention allow a person to perform a near-ideal biomechanical motion for double-poling. The first is that for a person using the present invention, the xe2x80x9coriginxe2x80x9d of the pulling movement is above and in front of the person. This allows the person during the double-poling movement to fully stretch (i.e., pre-load) his or her latissimus dorsi musclesxe2x80x94the main pulling muscles of the back. In addition, this xe2x80x9coriginxe2x80x9d allows the stomach and hip flexor muscles to be pre-loaded/stretched while the latissimus dorsi are fully extended, as well. Optimal power transfer is achieved when these muscle groups are stretched/pre-loaded as described.
The second key aspect of the present invention is that by the use of a flexible or pivotable connector, the hand grips of the present invention can follow the radial motion that the arms move through in the middle of the double-poling movement, even as the length of the pendulum is increased. Being a key to achieving the utmost skiing speed possible on snow, this lengthening of the effective radius of the arms is highly desirable. This feature of the apparatus of the present invention is critical to obtaining the near-ideal double-poling motion in a biomechanical sense.
The third key aspect of the present invention is that no support is provided (aside from grasping the handle ends) for the person""s body. This necessitates the natural ski-specific and harmonious coordination between the muscle groups involved. Virtually all previous ski-movement-emulating apparatuses support at least a portion of the user""s body. A consequence of supporting a portion of the body is that the muscle groups on either side of that supported body portion are isolated and cannot perform their xe2x80x98normalxe2x80x99 linking and stabilizing function during the movement. Deletion of these ski-specific functions significantly impairs the effectiveness of the exercise. This tends to counter the achievement of optimal double-poling technique as the hip flexors are not engaged, nor are the surrounding hip/pelvis stabilizers.